Waterproof foot coverings with molded-on (foamed-on) outersoles are commercially available and known.
Also known, in general, are films, membranes, laminates produced therefrom, etc., for the production of clothing articles that are waterproof but water vapor-permeable. It is possible to use them as inner linings, intermediate linings or also as outer material. A waterproof but water vapor-permeable layer here is thus also understood to mean a multi-layer planar structure, a laminate, etc. For the sake of simplicity, the waterproof but water vapor-permeable layer is frequently only designated as "waterproof layer" below. The designation "waterproof foot covering" herein means waterproof but water vapor-permeable foot covering.
Waterproof layers for producing waterproof but water vapor-permeable clothing articles, foot coverings and other articles are likewise known. A very well-known waterproof layer that is also very particularly suitable for the waterproof foot covering according to the invention is SYMPATEX.RTM..
In the production of waterproof foot coverings with molded-on (foamed-on) outersoles, there is the following problem: to obtain a high flexibility of the outersole (which is desirable in particular for children's shoes and children's boots), work is carried out at least partly without the otherwise conventional lasting margin that is adhesively bonded to the inner sole. This additionally provides cost advantages. Therefore, the lower welt region of the upper, the lower welt region of the waterproof layer and the outer welt region of the inner sole were therefore initially stitched together and subsequently the outersole was molded-on (foamed-on). With this method, however, the stitching material is not reliably embedded in a waterproof manner between the upper (outer material) and the waterproof layer (lining). As a result, water that has penetrated between the upper and the waterproof layer can penetrate, via the stitching material, into the interior, or foot region, of the foot covering. Hence, the stitching material, because of its wick effect, and the needle puncture points, because of their capillary effect, represent water bridges. There has therefore been no lack of attempts to find a practicable solution to this problem. These attempts have to some extent also been successful, at the cost, however, of other functional properties and/or of the cost advantages that were initially achieved in production.
In the case of a waterproof foot covering with molded-on (foamed-on) outersole, and in the production thereof, specifically the following four conditions have to be fulfilled:
(1) before the molding-on (foaming-on) of the outersole, the prefabricated foot covering consisting at least of the upper, the waterproof layer and the inner sole must form an essentially stable, handleable unit. In particular, there should be no displacement of the aforementioned parts with respect to one another either in the longitudinal direction, in the transverse direction or in the vertical direction of the foot covering. Such a displacement would subsequently be irreversibly fixed by the subsequent molding-on (foaming-on) of the outersole and would lead to a deformed, non-dimensionally-true foot covering.
(2) It should be reliably ensured that the lower seam or seams is/are waterproof in the critical region. This should be achieved only by the molding-on (foaming-on) of the outersole, not by previous sealing, adhesion bonding or the like.
(3) Once obtained, the waterproof property should also be maintained during use of the foot covering.
(4) Detachment of the lower welt region of the upper from the raised edge of the outersole should not occur during the use of the foot covering.